I have a horizontal tear in the fabric in one of my lower batten pockets, around 20cm long. The baton stays in the pocket and doesn't protrude, but I'd like to fix it before it gets worse. The sail is a second hand 5.4m2 Severne synergy.

Is this something I can fix myself? Gorilla tape? Sewing needle?

Nothing sticks to it well and hand sewing ain't fun.

melt the two ends a tiny bit with red hot needle or nail so it won't keep ripping and leave it
imho

cheapest is a strip of "ripstop spinnaker tape"
-rubbing alcohol before & clothes iron after if you wanna go all out fancy adhesion'sy-

this one had in me in stitches...homie Bert's handiwork...unsurpassed

I've used fiberfix mesh tape (from dr tuba) and aquasure FD glue, might not be pretty but it works well.

Thanks for the responses, figured I'd give an update.

I initially tried some sail repair tape however it game off after a few sessions - probably my fault.

Since then I've managed to rip the sail itself twice. I ended up using Gorilla Crystal Clear Tape on all the tears (strips on front and back) and it's held beautifully!